Vapor vacuum heating systems and integration with condensing vacuum boilers

ABSTRACT

In order to solve the numerous problems with existing steam, vacuum, and hot water heating systems, first presented is a novel system and method for a vapor vacuum system having low temperature condensate return which can operate without steam traps in both single-pipe and dual-pipe configurations. Secondly is disclosed systems and methods for integrating the disclosed vapor vacuum system with a condensing boiler. Thirdly is presented several systems and method of operating radiators having low temperature condensate return with the disclosed vapor vacuum system. Finally is presented condensing vacuum boiler designs that can be utilized with the disclosed vapor vacuum system. Also presented are embodiments having naturally-induced vacuum and utilizing district heat as well as combined heat and power. All innovations presented herein make vapor vacuum steam more efficient and economical for industrial, commercial, and home applications.

REFERENCE TO RELATED APPLICATIONS

This application is a non-provisional and claims the benefit of U.S.Ser. No. 61/702,533, filed on Sep. 18, 2012, entitled “Condensing boilerand vapor vacuum heating system combo,” the entirety of which is herebyincorporated by reference herein. This application is aContinuation-In-Part of U.S. Ser. No. 12/984,468, filed on Jan. 4, 2011,and entitled “Vapor/vacuum heating system,” which itself is anon-provisional of and claims the benefit of U.S. Ser. No. 61/338,341,filed on Feb. 18, 2010, and entitled “Vapor heating system withnaturally induced vacuum,” the entirety of both of which are herebyincorporated by reference herein.

FIELD OF THE INVENTION

The present invention relates to systems and methods for heating a spaceusing a vapor vacuum-based heating system having numerous improvementsover traditional vacuum systems. The present invention also relates toincreasing the efficiency of condensing boilers and allowing condensingboilers to be utilized with vapor vacuum heating systems.

BACKGROUND OF THE INVENTION

The statements in this section merely provide background informationrelated to the present disclosure and may not constitute prior art.

Existing positive low-pressure steam heating systems provide simple andreliable techniques for heating in a wide variety of industrial,commercial, and residential applications. Water (as a liquid) heated ina boiler becomes steam (a gas), which then rises through the feederpipes (conduits) and condenses in radiators, giving off its latent heat.Radiators become hot and heat up objects in the room directly as well asthe surrounding air. Steam is traditionally delivered under a lowpressure of up to 2 psig at 218° F. in order to improve boiler safetyand efficiency. Additionally, steam at lower pressure moves faster,contains less water, and doesn't create boiler low water problems. Theboiler creates the initial steam pressure to overcome friction in thefeeder pipes.

An existing steam system can be converted to a vapor (steam) vacuumsystem by operating the steam system under 5-10 inches of Hg vacuum.Although there are some efficiency gains, the conversion of a steamsystem into a vacuum system results in an increased maintenance cost dueto additional vacuum equipment, condensate pumps, and electricity usage.In existing vacuum systems, steam traps are utilized in which condensateis separated from steam, sucked by a vacuum pump, and returned into thesystem by a water pump. Steam trap usage is also a major maintenance,repair, and replacement problem. Few new vacuum systems have beeninstalled in the last fifty years due to high installation andmaintenance costs.

Existing steam (vapor) systems are robust and reliable but have multipleproblems, including high installation costs, noise, uneven heatdistribution, and control difficulties. Therefore, many worn out steamsystems are being retrofitted into hot water heating systems. However,such retrofits are very expensive because the boiler and the oldplumbing have to be replaced which requires significant demolition ofbuilding internals. Alternatively, the level of building destruction ismuch less for conversion of a steam into a vacuum system and theexisting boiler can be utilized. Therefore, a low-cost and efficientvacuum system would be an advantageous alternative for steam systemretrofits as well as for new heating system installations.

In order to boost energy efficiency, modern hot water condensing boilersabsorb the latent heat of water vapor from the flue gas. The recommendedtemperature of the water return (supply into boiler condensing section)is below 100° F. in order to condense most of the water from the fluegas. In reality, this temperature is at 140° F. or above for most of theheating season in order to deliver enough heat into the building. As aresult, benefits of condensing mode usage are lost. Another problem ofhot water condensing boilers is limited temperature of supply water. Thetypical temperature drop through a hot water heating system is 20° F.,and therefore for condensing boilers, supply water temperature islimited to 120-160° F. At such low temperatures, the energy value ofdelivered heat is less than in a regular hot water system. This resultsin hot water condensing boilers that operate as traditional boilers withtheir condensing section inefficient for most of their operating time,eliminating the energy saving benefits of condensing boilers almostentirely while still having their high capital costs.

The temperature of condensate return in existing vacuum systems iseither equal to the temperature of vapor rising through the same pipe orslightly lower in two pipe systems. The high temperature of condensatereturn is considered an inherent feature of the system and neverchallenged. Steam and vacuum systems are never used with condensingboilers, and therefore no steam or vacuum condensing boilers exist.Accordingly, as recognized by the present inventor, what are needed area novel system and method for a vapor vacuum system having lowtemperature condensate return. What are also needed are a system andmethod for integrating a vapor vacuum system with a condensing boiler.As recognized by the present inventor, what is also needed is a vacuumcondensing boiler that can be utilized with the vapor vacuum system.

Therefore, it would be an advancement in the state of the art to providean apparatus, system, and method for a low temperature vapor system aswell as ways to integrate such systems with condensing boilers. It wouldalso be an advancement in the state of the art to provide a vacuumcondensing boiler to work with such a system.

It is against this background that various embodiments of the presentinvention were developed.

BRIEF SUMMARY OF THE INVENTION

Accordingly, a preferred embodiment of the present invention is aheating system integrating a closed-loop two-pipe vapor vacuumdistribution system having periodic condensate return and a vapor vacuumcondensing boiler (shown in FIG. 6), the system comprising a vaporsource adapted to generate vapor, the vapor source comprising anevaporating section and a condensing section; one or more radiatorscomprising a heat activated valve at an exit from each radiator, thevalve set to close at approximately 100° F. to prevent hot condensatefrom entering into the condensing section; a feeder conduit connectingsaid vapor source to said radiators; a return conduit for returningcondensate from each radiator back to said vapor source, wherein saidreturn conduit contains no steam traps; a vacuum pump to evacuate airfrom the system to a vacuum level, wherein the vapor source, the feederconduit, and the return conduit are air-tight; a temperature sensoradapted to sense a temperature of the vapor leaving the vapor source; apressure sensor adapted to sense a pressure of the vapor source; and acontrol unit for controlling the condensing steam boiler and the vacuumpump based on the temperature and the pressure sensed by the temperaturesensor and the pressure sensor to maintain a predetermined vacuum leveland a predetermined temperature of the vapor, wherein the return conduitreturns said condensate from the radiators to the condensing section ata temperature below approximately 100° F. sufficient for condensingwater from flue gas from a burner in the vapor source.

Another embodiment of the present invention is the system describedabove, where air is evacuated by the vacuum pump when the vapor sourceis idle at a vapor source temperature below approximately 100° F. whenthe pressure measured in the pressure sensor is above a predeterminedthreshold.

Yet another embodiment of the present invention is the system describedabove, also including a thermostat in a space to be heated, wherein thevapor source is switched on and off by the control unit until atemperature in the space to be heated is equal to a thermostat settemperature.

Yet another embodiment of the present invention is the system describedabove, also including a backflow valve on a condensate return line at anentrance into the condensing section to prevent water backflow into thecondensate return line.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level in an idle system at a temperature in thevacuum condensing boiler below around 100° F. is up to 29 inches Hg.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level and corresponding temperature of the vaporsource is adjusted based on an outside temperature, and wherein a loweroutside temperature results in a higher operating pressure and acorresponding higher temperature of the vapor source.

Yet another embodiment of the present invention is the system describedabove, where at least one radiator comprises a build-in heat activatedvalve adapted to close a radiator entrance when a condensate returntemperature exceeds approximately 100° F.

Yet another embodiment of the present invention is the system describedabove, where the build-in heat activated valve comprises a capsulepositioned at the radiator bottom and filled with a low boiling fluid(or wax), and said capsule is connected by a capillary to a bellow whichexpands and closes the radiator entrance when the capsule is heatedabove a set temperature.

Yet another embodiment of the present invention is the system describedabove, also including a set of valves on the vapor source adapted tosplit the system into a heated part, connected to the evaporatingsection, and a cooling part, connected to said condensing section,wherein a movement of the set of valves reconnects the cooling part tothe evaporating section and the heated part to the condensing section,reversing system operation, without stopping boiler operation.

Yet another embodiment of the present invention is the system describedabove, where the feeder conduit from the vapor source to the radiatorsand the return conduit are made from thermoplastic tubing ornoncorrosive copper.

Another embodiment of the present invention is a heating system having aclosed-loop two-pipe vapor vacuum distribution system having periodiccondensate return (shown in FIG. 3), the system comprising a vaporsource adapted to generate vapor; one or more radiators, each radiatorcomprising a check valve on a radiator condensate return line adapted toperiodically return condensate from the radiator, wherein at least oneradiator entrance comprises a control valve adapted to control vaporflow into the radiator based on a temperature in the radiator'slocation; a feeder conduit connecting said vapor source to saidradiators; a return conduit for returning condensate from each radiatorback to said vapor source, wherein said return conduit contains no steamtraps; a vacuum pump to evacuate air from the system, wherein the vaporsource, the feeder conduit, and the return conduit are air-tight; atemperature sensor adapted to sense a temperature of the vapor leavingthe vapor source; a pressure sensor adapted to sense a pressure of thevapor source; and a control unit for controlling the vapor source andthe vacuum pump based on the temperature and the pressure sensed by thetemperature sensor and the pressure sensor to maintain a predeterminedvacuum level and a predetermined temperature of the vapor.

Yet another embodiment of the present invention is the system describedabove, where air is evacuated by the vacuum pump when the vapor sourceis idle when the pressure measured in the pressure sensor is above apredetermined threshold.

Yet another embodiment of the present invention is the system describedabove, also including a backflow valve on a condensate return line ofthe vapor source to prevent water backflow into the condensate returnline.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level in an idle system at a temperature in thevacuum condensing boiler below approximately 100° F. is up to 29 inchesHg. In some embodiments, the vacuum level is at least 20 inches Hg, andmore preferably at least 25 inches Hg, and even more preferably at least29 inches Hg.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level and a corresponding temperature of thevapor source is adjusted based on an outside temperature, and wherein alower outside temperature results in a higher operating pressure andcorresponding higher temperature of the vapor source.

Another embodiment of the present invention is a heating system having aclosed-loop two-pipe vapor vacuum distribution system (shown in FIG. 2),the system comprising a vapor source adapted to generate vapor; one ormore radiators; a feeder conduit connecting said vapor source to saidradiators; a return conduit for returning condensate from each radiatorback to said vapor source, wherein said return conduit contains no steamtraps; a vacuum pump to evacuate air from the idle cooled system to avacuum level of at least 20 inches Hg, (more preferably at least 25inches Hg, and most preferably at least 29 inches Hg), wherein the vaporsource, the feeder conduit, and the return conduit are air-tight; atemperature sensor adapted to sense a temperature of the vapor leavingthe vapor source; a pressure sensor adapted to sense a pressure at anexit of the vapor source; and a control unit for controlling the vaporsource and the vacuum pump based on the temperature and the pressuresensed by the temperature sensor and the pressure sensor to maintain aconsistent vacuum level and a consistent temperature of the vapor.

Yet another embodiment of the present invention is the system describedabove, where air is evacuated by the vacuum pump when the vapor sourceis idle when the pressure measured in the pressure sensor is above apredetermined threshold.

Yet another embodiment of the present invention is the system describedabove, also including a backflow valve on a condensate return line ofthe vapor source to prevent vapor from entering the condensate returnline.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level in an idle system at a temperature in thevacuum condensing boiler below approximately 100° F. is up to 29 inchesHg.

Yet another embodiment of the present invention is the system describedabove, where the vacuum level and a corresponding temperature of thevapor source is adjusted based on an outside temperature, and wherein alower outside temperature results in a higher operating pressure andcorresponding higher temperature of the vapor source.

Other embodiments of the present invention include methods correspondingto the systems described above, as well as methods of operation of thesystems described above. Other features, utilities and advantages of thevarious embodiments of the invention will be apparent from the followingmore particular description of embodiments of the invention asillustrated in the accompanying drawings, in which like numeralsindicate like elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a schematic of a single-pipe vapor vacuum system withperiodic condensate return according to one embodiment of the presentinvention.

FIG. 2 illustrates a schematic of a two-pipe vapor vacuum heating systemadapted to operate without steam traps according to another embodimentof the present invention.

FIG. 3 illustrates an operation of the two-pipe vapor vacuum heatingsystem operating with control valves on supply lines and check valves oncondensate return lines according to yet another embodiment of thepresent invention.

FIG. 4 illustrates a thermal efficiency of a hot water condensing boilersystem as a function of return condensate temperature.

FIG. 5 illustrates a thermal image of a flat panel radiator according toone embodiment of the present invention during an operational test run.

FIG. 6 illustrates one method of integrating a vapor vacuum systemaccording to the present invention with a vacuum condensing boileraccording to another embodiment of the present invention.

FIG. 7 illustrates a schematic of a vapor vacuum heating system havingmultiple risers and a control manifold/set of valves according to yetanother embodiment of the present invention.

FIG. 8 illustrates a schematic of an improved flat panel radiator with abuild-in heat-activated valve (HAV) according to another embodiment ofthe present invention for use with a vapor vacuum heating system.

FIG. 9 illustrates a schematic of an enclosed control valve according toone embodiment of the present invention for use with a vapor vacuumheating system.

FIG. 10 illustrates a schematic of one embodiment of a vacuum condensingboiler according to another embodiment of the present invention.

FIG. 11 illustrates a schematic of another embodiment of a vacuumcondensing boiler according to yet another embodiment of the presentinvention.

FIG. 12 illustrates a schematic of yet another embodiment of the presentinvention in which a single-pipe vapor vacuum heating system isintegrated with a vacuum condensing boiler.

FIG. 13 illustrates a schematic of an embodiment of a radiator designhaving a temperature controlled sliding member for controlling atemperature profile in the radiator according to yet another embodimentof the present invention.

FIG. 14 illustrates a schematic of an embodiment of a large system withnaturally induced vacuum according to yet another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The following description is merely exemplary in nature and is in no wayintended to limit the present disclosure, application, or uses.

In order to solve the aforementioned problems with conventional steam,vacuum, and hot water heating systems, first is presented herein is anovel single-pipe vapor vacuum system having a low temperature periodiccondensate return. Second is presented an embodiment of a two-pipe vaporvacuum system without steam traps. Third is disclosed systems andmethods for integrating the two-pipe vapor vacuum system with acondensing boiler. Fourth is presented several systems and method ofoperating radiators with the vapor vacuum system to ensure lowtemperature condensate return. Fifth are presented several designs forcondensing vacuum boilers that can be utilized with the low temperaturevapor vacuum system. Sixth is presented a single-pipe vapor vacuumsystem integration with a condensing boiler. Finally is presented anembodiment of the present invention with a naturally induced vacuum.Certain embodiments will now be described in order to provide an overallunderstanding of the principles of the structure, function, manufacture,and use of the devices and methods disclosed herein. The featuresillustrated or described in connection with one embodiment may becombined with the features of other embodiments.

The vapor vacuum system of the present invention can be used in anybuilding and/or dwelling as needed. For the purposes of the descriptionsherein, the term “building” will be used to represent any home,dwelling, office building, and commercial building, as well as any othertype of building as will be appreciated by one skilled in the art. Forpurposes of this description, “steam” and “vapor” are usedinterchangeably. “Single-pipe” and “one-pipe” are used interchangeablyand refer to systems with a single pipe used for both feeding vapor tothe radiators and returning condensate. “Two-pipe” and “double-pipe” areused interchangeably to refer to systems in which a separate pipe isused to return condensate from the pipe used to feed the vapor to theradiators. As used herein, “closed-loop,” “closed loop,” and “closedsystem” are used interchangeably to mean an essentially closed vacuumsystem and piping with essentially air-tight connections and negligibleleakage. The term “steam system” shall refer to positive pressure steamsystems, usually operating at up to 2 psig, whereas the terms “vaporvacuum system,” “vacuum system,” “vapor vacuum heating,” and “VVH” shallrefer to negative pressure steam systems operating with at least 5inches Hg vacuum.

Single-Pipe Vapor Vacuum Systems with Periodic Condensate Return

First, a vapor vacuum heating system with a cycling steam (vapor) sourceused with a plurality of radiators having periodic condensate return ispresented. During a heating cycle, condensate is retained in radiatorsand released later through steam supply line. Such condensate and steamflow alternation eliminates water hammering and justifies usage ofsmaller diameter tubes and new radiator design. Under vacuum, the systemoperates like a branched heat pipe with periodic condensate return. In aheat pipe, heat is captured as liquid evaporates at one end, andreleases the heat when the vapor condenses at an opposite end. In oneembodiment, the system may include a vacuum pump to evacuate air fromthe system. In another embodiment, the system may include a vacuum checkvalve on air vent lines and operational procedure to create vacuumnaturally by steam condensing in a closed space after complete airpurging from the system. The vapor source's cut off pressure can beadjusted to regulate the vapor's temperature depending on the outsidetemperature.

Temperature control for steam/vacuum systems includes a thermo-regulatorin the room farthest from the boiler. Because of higher pressure drop inthe pipe, this room is the last one to receive heat, and the boilershuts off when a set temperature is achieved. Therefore, rooms closestto the boiler are overheated and usually cooled by open windows, whilethe most distant rooms are under-heated. Uneven steam distribution andbuilding overheating are common problems of such steam heating,especially for single-pipe systems. It is estimated that for every 1° F.increase of internal temperatures, the space heating cost increases by3%. In summary, an ordinary building's overheating by 14° F. (average 7°F.) corresponds to around 21% more fuel consumption and implies 21%higher heating bills.

To decrease the system's pressure drop and achieve uniform steamdistribution, large diameters steel pipes with thick threaded walls havebeen utilized. In addition, reduced steam velocity in such pipes helpsto avoid water hammering when steam and condensate are counter-flowing.Unfortunately, the usage of large diameter heavy steel piping has causedsignificant problems, including:

(1) Steam supply lines should be preheated to a saturated steamtemperature before any steam is delivered into the radiator; the lineshould be kept at this temperature for the duration of the heatingcycle. The average 33.3% difference between the boiler's “gross” and“net” is the heat it takes to bring the system piping up to the steamtemperature. “Net” is the heat available to the radiators after thesteam has heated the pipes.

(2) The choice of a radiator is limited to heavy cast iron models; theseradiators require a long time to heat up and continue to emit heat intothe room long after the set temperature is reached and the burner isdeactivated.

(3) Expensive installation

(4) High heat loss

Converting steam heating systems into known vacuum systems improves heatdistribution and system efficiency, but adds maintenance and repairproblems. Converted steam systems maintain vacuum at 5-10″ Hg, andemploy original heavy steel piping, and cast iron radiators; newinstallation of such vacuum systems would be very expensive.

The entry of forced air systems into the U.S. market shattered thedominance of steam, vacuum, and hot-water heating. The superior qualityand efficiency of radiant heat was sacrificed for convection heating,all for the sake of a lower installation cost. Few steam or vacuumheating systems were installed during the last fifty years. Still, manybuildings in the U.S. and abroad are heated by steam from either boilersor district systems. Significant savings can be achieved by convertingsuch steam systems into vacuum vapor systems according to someembodiment of this invention. For new high-rise buildings, steam isoften a valid choice because of the problems associated with long airducts (for forced air systems) and with high pressure (for water heatingsystems).

According to one embodiment of the present invention, what has beendeveloped is a system and method for preventing water hammering in asingle-pipe steam heating system by condensate retention in the radiatorduring the heating cycle and release into the boiler afterward. In oneembodiment, a steam (vapor) source is provided for producing andintroducing steam into the systems described herein. The steam sourcemay be any source known in the art capable of heating water to producesteam, including a boiler system located within the building, or anexternal district heating system, heat from power generation, waste heatfrom industry, and other systems known to provide steam.

A common principle of steam heating operation assumes continuouscondensate return into the boiler either through the inlet pipe (“feederconduit” for single-pipe systems) or via a separate line (“returncondensate line” in two-pipe systems). A single pipe system usuallyemploys large diameter pipes in order to avoid water hammering and thatrequirement subsequently worsens system efficiency, comfort, control,etc. This problem can be resolved by an embodiment of the presentinvention having a periodic condensate return from the radiators aftereach heating cycle as shown in FIG. 1.

The system of such an embodiment can be modeled conceptually as abranched “heat pipe,” but without a wick and, therefore, no restrictionon length. As shown in FIG. 1, while steam is entering into the uppersection of radiator 102, condensate accumulates at the bottom and isreturned into the steam supply line through condensate flow controlvalve 103 after heating cycle. Either a float check valve, athermostatic valve, a zero pressure check valve, or another suitablevalve can be used to control condensate return cycles; bubble tightperformance is not crucial. Steam delivery can be regulated by a controlvalve 104 per radiator base (R111, R112, R123) or by a zone controlvalve 105 per radiator group (R121, R122). The system is connected to avacuum pump 106 through a vacuum pump control valve 107. In oneembodiment, a steam ejector may be utilized to create an initial vacuumin the system; this makes the system self-sufficient and lesselectricity dependent. Proper plumbing pitch directions 108 should beprovisioned for condensate return into the boiler by gravity. Such anarrangement facilitates periodic condensate return only after boiler 101stops. The benefits of this embodiment of the present invention include:

(1) Hot condensate retaining in the radiator during the heating cycleadds heat into the space to be heated.

(2) After the boiler shut off, the vapor from the boiler continues todeliver heat into the radiators until the vacuum is formed in the systemand equilibrium is established.

(3) Turbulent vapor flow regime in smaller diameter tubes ensures thatcondensate droplets will be carried into the radiator.

(4) Tubes of smaller diameters can be easily connected with fewerfittings and less leaks.

(5) Operating under higher vacuum (up to 29″ Hg or even higher), andutilizing modern plumbing, radiators, and a control models, rather thanthe existing vacuum systems operating at 5-10″ Hg.

Saturated water vapor pressure in the boiler is a function oftemperature and vice versa (Table 1). The vapor temperature at theradiators' entrances (and therefore the temperature of the radiators)can be controlled in a broad range by the temperature/pressure settingof the boiler. For example, at 2 psi pressure drop in the tubing and aboiler pressure of 10.3 psia, vapor will enter into the radiators at 8.3psia@184.6° F., and at boiler pressure of 9.3 psia, vapor will enterinto the radiators at 7.3 psia@178.9° F., correspondingly. So theradiators' temperature can be controlled by changing temperature/vacuumlevel in the boiler.

TABLE 1 Properties of Saturated Steam Saturated Steam Pressure Pressurein System Temperature (inch Hg) inch Hg psia ° F. ° C. 0.0 29.74 0 320.0 5.7 24 2.8 140.3 60.2 10.7 19 5.3 165.2 74.0 12.7 17 6.3 172.5 78.114.7 15 7.3 178.9 81.6 16.7 13 8.3 184.6 84.8 18.7 11 9.3 189.7 87.620.7 9 10.3 194.4 90.2 22.7 7 11.2 198.8 92.7 29.7 0 14.7 212 100.0

Similar to modern air conditioning applications, a vacuum in thisleak-tight system is created once by a vacuum pump and restored on rareoccasions. Alternatively, achieving and maintaining a vacuum level of26-29″ Hg (versus 29.9″ Hg for air conditioning application) is simpler,less expensive, and the water vapor is not an environmental pollutant(unlike Freon and other chlorofluorocarbons used in air conditioningsystems).

Depending on the outside conditions, the temperature of the vaporsupplied into the radiators may be adjusted by controlling the systemoperating interval in the vacuum; the deeper the vacuum, the lower thevapor's temperature. Modern copper plumbing is warranted for many years,so the system dependency on the tightness to leaks and, therefore, onelectricity for vacuum pump is reduced. In one preferred embodiment,polysulfone type tubing can be utilized for steam conduit and flexibleTeflon type tubing for end-point connections to radiators; boththermoplastics' properties exceed the vacuum heating system operationalparameters.

Two-Pipe Vapor Vacuum Systems without Steam Traces

Second is presented an embodiment of a two-pipe vapor vacuum systemwithout steam traps. In a typical vacuum heating system, steam trapsand/or thermostatic steam traps, are utilized like in a steam system.The purpose of conventional steam traps is to periodically releasecondensate back into the boiler and to prevent steam from entering intoreturn lines. Such steam traps are a major maintenance problem requiringroutine inspections, repairs, and replacement.

One embodiment of the vapor vacuum system, operating in vacuum/pressureinterval from initial vacuum of 28-29″ Hg and up to 2 psig (recommendedmaximum pressure for steam systems), was tested with lightweight supplylines and radiators as shown in FIG. 2. Vacuum was created initially andrestored (if necessary) by vacuum pump 202, and check valve 201 was usedto prevent boiler backflow. It was found that the vapor vacuum systemaccording to one embodiment can operate successfully without steamtraps. Vacuum, created in each radiator by condensing vapor, keeps thecondensate from leaving the radiator in the form of a natural plug atthe radiator bottom. Because of the short heat cycle period, the levelof accumulated condensate is not significant enough to reduce radiatorheat transfer area. When the radiator is heated from top to bottom as inradiators R221 and R222, the pressure of saturated vapor inside theradiator increases, and vapor from the boiler is directed to other lessheated radiators R223 and R224. The boiler stops when thepressure/temperature rises to an upper set point, the pressure equalizesin the idle system and condensate returns by gravity from each radiator.When the boiler temperature drops to a low set temperature (orcorresponding pressure), another heating cycle starts until the settemperature in a heated space is achieved. Accordingly, in oneembodiment, no steam traps are necessary.

This natural heat distribution balance can be disrupted if supply lineis closed by flow control valve on any radiator. As an example, shown inFIG. 3, vapor from nearby radiator R333 will enter radiator R331 througha condensate return line if a control valve 303 is closed. To preventvapor entering the condensate return line, each radiator is equippedwith a float ball check valve 304. When the radiator is heated from topto bottom during the heating cycle, the ball is pressed down, and thefloat ball check valve is closed (FIG. 3, insert 308). When the boilerstops and pressure/vacuum equalize throughout the system, the ballfloats and releases condensate to the boiler (FIG. 3, insert 309). Incontrast to traditional steam traps, in a float ball check valve, thereis no intermediate condensate release during heating cycle. A float ballcheck valve is employed for condensate handling on each radiator; thissimple, reliable, and inexpensive device works consistently, whether thesystem is working under pressure or under a vacuum. Because vapor andcondensate flow are alternating on the same line, water hammering can beprevented, which allows for the usage of smaller diameter tubing.Optionally, and according to alternative embodiments of the presentinvention, heat activated valves may be utilized on condensate returnlines instead of float ball valves. As in FIG. 2, vacuum was createdinitially and restored (if necessary) by vacuum pump 302, and checkvalve 301 was used to prevent boiler backflow.

Therefore, one embodiment of the present invention eliminates the needfor steam traps, which are expensive inspection and maintenance problemsfor steam and existing vacuum heating systems.

Accordingly, one embodiment of the present invention is a vapor vacuumheating system with a plurality of radiators, comprising a vapor source;a feeder conduit connecting said vapor source to the radiators; acondensate return conduit having no steam traps on each radiatorconnected to said feeder conduit; a float ball check valve on saidcondensate return conduit to prevent vapor entering condensate returnline during the heating cycle and releasing condensate after the heatingcycle; a vacuum pump to evacuate the system; a thermostat in the spaceto be heated; a vapor source control unit; and a pressure sensor forgenerating a signal to the vapor source control unit, wherein an airfrom the system is evacuated by the vacuum pump, and wherein the vaporsource is switched on and off by the vapor control unit within presetpressure until the temperature in the space to be heated is equal to athermostat set temperature.

Two-Pipe Vapor Vacuum System Integration with Condensing Boilers

Third is disclosed systems and methods for integrating the two-pipevapor vacuum system with a condensing boiler (CB).

In order to boost energy efficiency, modern hot water CB absorb thelatent heat of water vapor from the flue gas. Recommended temperature ofwater return temperature (supply into boiler condensing section) isbelow 100° F. in order to condense most of the water (see FIG. 4,adapted from T. H. Durkin, “Boiler System Efficiency,” ASHRAE Journal,vol. 48, July 2006, p. 51). In reality, water return temperature is at140° F. level for most of the heating season in order to deliver enoughheat into building. As a result, benefits of condensing mode usage arelost. Another problem of hot water CB is limited temperature of supplywater. Typical temperature drop through hot water heating systems is 20°F. and therefore for CB supply water temperature is limited to 120-160°F. At such low temperatures, the energy value of delivered heat is lessthan in regular hot water systems.

The temperature of condensate return in traditional vacuum single-pipesystems is either equal to the temperature of vapor rising through thesame pipe or slightly lower in two pipe systems. The high temperature ofcondensate return is considered an inherent feature of traditionalvacuum and steam systems and is never challenged. The present inventorhas recognized that lowering the temperature of condensate return wouldimprove system efficiency and reduce heat losses.

Typical thermal images of the radiator in the proposed two-pipe vaporvacuum system are shown in FIG. 5 after the boiler was stopped at 10″ Hg(after 7 and 20 minutes, 501 and 502, respectively). It shows theremarkably even temperature of the heated area at the radiator top andarea of low temperature at the bottom. The phenomenon can be explainedby the fact that latent heat of water evaporation/condensationrepresents 85-90% of total vapor heat. Due to this, a small portion ofthe radiator surface is sufficient to cool the condensate to roomtemperature (dissipate heat of saturated liquid). This test findingsuggested a possible way to improve the system's efficiency byintegrating condensing boiler technology into the vapor vacuum heatingsystem.

In the vapor vacuum system described in this application, the “returntemperature versus efficiency” dilemma can be resolved. Condensingboiler integration into vapor vacuum system not only eliminatesrestrictions on operation parameters (which are imposed in hot watersystems), but can also add significant benefits in design, safety,maintenance, efficiency and installation costs. The vapor vacuum systemdescribed in this application can keep radiators hot up to 212° F. andyet still return condensate at temperatures below approximately 100° F.into the condensing section at the same time.

The various vapor vacuum heating systems presented herein can beintegrated with a condensing boiler, to create overall system efficiencyimprovements. Such a system comprises a condensing boiler, at least oneradiator located in the space to be heated, an apparatus (vacuum pump,steam ejector, etc.) to evacuate air from the system, vapor transferline(s) extending between the boiler and the radiator(s), and returnline(s) for condensate return. The boiler oscillates within a predefinedvacuum/temperature interval until a set temperature is achieved.Condensate from the radiator(s) is returned back by gravity into theboiler's condensing section. Several methods are proposed to reduce thetemperature of radiators' condensate return into the boiler in order tointegrate the system with condensing boilers. Later, a design for avacuum condensing boiler which can be utilized with the presentinvention is presented.

In one embodiment of the present invention, the various embodiments ofthe vapor vacuum heating systems described in this application may beintegrated with a condensing boiler. A schematic of a two-pipe vaporvacuum heating system integration with a condensing boiler according toone embodiment of the present invention is shown in FIG. 6. Thecondensing boiler comprises a burner 606, an evaporating section 607,and a condensing section 608. In one embodiment, each radiator isequipped with a heat activated valve (HAV) 601 at an exit of thecondensate return line. During the heating cycle, HAV 601 at the exit ofthe hottest radiators (radiators R661, R662 which are nearest to theboiler) are closed, and hot condensate is accumulating at the bottom. Atthe same time, condensate flows back into the boiler from partiallyheated radiators R663, R664. Zone control valve 602 and radiator controlvalve 603 can be utilized for heat distribution control. Vacuum in thesystem is created and maintained by a vacuum pump 604, and check valve605 prevents hot water backflow from boiler during heating cycle.

In a two-pipe vacuum system with multiple risers, a manifold (set ofvalves) can be utilized to alternate heat supply into the multiplerisers. An example of a two-riser system is shown in FIG. 7. Thecondensing boiler comprises a burner 706, an evaporating section 707,and a condensing section 708. While radiators R771 and R772 on riser 701are receiving heat, vacuum is naturally created in cooling radiatorsR773 and R774 on riser 702, and vise versa (when manifold 703 turns).The frequent boiler on/off switching can be reduced for multiple-sectionsystems. Condensate from radiators returns through heat activated valves(HAV) 705 on each radiator (or solenoid or check valve) into condensingsection 708 of the boiler in an idle system. Vacuum in the system iscreated and maintained by a vacuum pump 704, optionally vacuum can berestored in a separated cooled section 702. Check valve 709 prevents hotwater backflow from boiler during heating cycle. If required, manifold703 can be utilized to close boiler vapor supply line completely, andvacuum level in the system can be restored by vacuum pump withoutwaiting for boiler cooling to 100° F.

The efficiency of the regular non-condensing steam boilers integratedinto a two-pipe vacuum heating system is expected to improve due tooperation in vacuum, lower temperature of return condensate, and abilityto control vapor temperature depends on the outside temperature. In someembodiments, it is possible to use the proposed system with regularnon-condensing boilers; the condensing section elimination from theboiler would benefit the boiler maintenance, life expectancy, and cost.

In some embodiments, instead of a boiler, other heat sources may beutilized for the vapor vacuum system described herein, such as districtheating, micro-turbine exhaust, heat and power cogeneration heat, wasteheat, geothermal, solar, etc.

Radiator Designs Having Low Temperature Condensate Return

Fourth are presented several systems and method of operating radiatorswith the vapor vacuum system to ensure low temperature condensatereturn.

A schematic of a flat panel radiator with a build-in heat-activatedvalve (HAV) is shown in FIG. 8. The valve includes a bellow 801connected by a capillary 802 to a capsule 803 containing a lowtemperature boiling fluid (such as pentane, acetone, etc) or wax inside.When the radiator bottom gets hot, the condensate heats the capsule andthe evaporated liquid/wax expands the bellow 801 to close radiator (asshown in FIG. 8, part B). When the radiator bottom cools down, condensedliquid drains back into the capsule 803 and the contracted bellow 801opens the radiator entrance (FIG. 8, part A). During the heating cycle,the valve occasionally opens and closes, keeping the radiator heatingarea hot and condensate temperature low. The valve is inserted through aradiator plug 804, into a position fixed by nibs 805 and can be easilyaccessed for inspection and/or replacement. The bellow type valvedescribed here may be a reliable and economical alternative to the HAV.In one embodiment, a backup HAV at each radiator exit is an optionalsafety feature.

A room/zone temperature controller coupled with a solenoid valve is acommon solution today for building's heat distribution control, but theseal on the valve stem usually develops leaks with time and usage. Inone embodiment, the problem may be resolved with a new enclosed valvedesign for a vapor supply line into radiators as shown in FIG. 9. Amagnet 903 inside plastic tube 901 and induction coil 902 is locked intoorifice seat 904 by a retractable mechanism and spring 905 to blockvapor flow. In some embodiments, a turning movement may be added toextend life-time. These valves are not expected to close the supply linebubble-tight, but 90-95% of passage closing would suffice to controlheat distribution. FIG. 9 (left), shows the valve open, and FIG. 9(right) shows the valve closed.

In summary, heat distribution through the system is controlled byradiator size (heating area), HAV which is either build-in or located oncondensate return line, room controllers, and boiler operatingparameters adjusted to the outside temperature.

The system according to this embodiment has the following majordifferences relative to a single-pipe VVH:

(1) Condensate return line(s) from the radiators to the boilercondensing section, in which plastic tubing can be employed because ofthe low temperature condensate return.

(2) HAV on condensate return line from each radiator. Optionally, abackup HAV at the condensate entrance into boiler condensing section maybe used to prevent radiators' HAV malfunction; and paper thermometerindicators on each condensate return line can be used to locate a failedHAV.

Vacuum Condensing Boiler Designs

Fifth are presented several designs for condensing vacuum boilers thatcan be utilized with the low temperature vapor vacuum system. Since thevarious vapor vacuum system embodiments according to the presentinvention allow integration of condensing boilers for the first time,vacuum condensing boilers are desirable for use with the presentinvention. Because of the various embodiment innovations described inthis application, vapor vacuum heating systems with vacuum condensingboilers are feasible to use for the first time. Accordingly, embodimentsof the present invention also include vacuum condensing boilers asdescribed below. Various condensing boiler designs are envisioned to beuseable with the present vapor vacuum system, and the particularcondensing boiler designs are not intended to limit the scope of thepresent invention.

An attractive feature of the vapor vacuum heating system is advancedheat transfer conditions. Heat transfer coefficients in the boiler arechanged by orders of magnitude depending on temperature differencesbetween the wall and boiling temperature of the saturated liquid(Farber-Scorah Boiling Curve, see, for example, FIG. 6.14 in P. K. Nag,Heat and Mass Transfer, 2nd Ed., 2007 and FIG. 5.1 in M. L. Corradini,Fundamentals of Multiphase Flow, 1997). Hot water boilers work in theleast efficient regime of interface evaporation (pure convection).Furthermore, in hot water systems, the “bubbles” regimes, which have thehighest heat transfer coefficients, are avoided because the hot watercirculation worsens in the presence of the vapor phase. Conversely, in avacuum system, heat transfer instantly occurs in the most efficient“bubbles” regime because water boils at lower temperatures. Therefore,the required heat exchange area can be reduced significantly not only inthe boiler evaporative section, but also in the boiler condensingsection.

FIG. 10 illustrates a schematic of a vacuum condensing steam boiler witha single pass down flow configuration according to one embodiment of thepresent invention. Two- and three-pass apparatus may be used as well.High temperature flue gas from a burner 1006 evaporates water in aboiler cylindrical evaporating section 1001 and then flows down into acondensing section 1002 along a spiral tube heat exchanger 1005 filledwith condensate return from the radiators. Air 1008 and fuel 1009 aresupplied from the boiler top; an air blower 1007 is utilized to startthe system. Cold condensate 1012 from radiators enters into the spiraltube heat exchanger 1005 from the bottom of the boiler and rises up dueto hot water's lower density, boils, and exits the boiler as vapor phase1013. Condensate 1012 from the radiators periodically returns into theboiler through a back flow valve 1004 when the boiler stops and thesystem pressure equalizes. To avoid a sharp decrease in the heattransfer in the evaporating section due to transition into film boiling,fins 1003 are provisioned to direct vapor phase outward from the heatexchange area in the evaporating section 1001 of the boiler. Flue gas1010 leaves the boiler bottom through an exhaust line, while flue gascondensate 1011 is removed from the boiler bottom through a separateline.

In one alternative embodiment of the vacuum condensing boiler, an arrayof short thick wall heat pipes can be utilized in the condensing sectioninstead of the spiral tube heat exchangers, as shown in FIG. 11. Hightemperature flue gas from a burner 1106 evaporates water in a boilercylindrical evaporating section 1101 and then flows down into acondensing section 1102. Heat pipes 1105 are threaded through the innerwall of the condensing section 1102. These heat pipes have no wickcapillary structure; instead, they comprise short, closed-end tubes witha working liquid under vacuum (water can be used as a working liquid insome embodiments). The condensing section 1102 comprises twosemi-cylinders 1108 connected to the evaporating section 1101 by lines1109 that can be taken apart for the heat pipes' inspection andreplacement. Although the tips of these heat pipes 1105 will be exposedto corrosive flue gas, the condensing section 1102 would still befunctional if the walls of one or several heat pipes fail. Air 1110 andfuel 1111 are supplied from the boiler top; an air blower 1107 isutilized to start the system. Cold condensate 1114 from the radiatorsenters from the bottom of the boiler and rises up due to hot water'slower density, boils, and exits the boiler as vapor phase 1115.Condensate from the radiators periodically returns into the boilerthrough a back flow valve 1104 when the boiler stops and the systempressure equalizes. To avoid a sharp decrease in the heat transfer inthe evaporating section 1101 due to transition into film boiling, fins1103 are provisioned to direct the vapor phase outward from the heatexchange area in the evaporating section of the boiler. Flue gas 1112leaves the boiler bottom through an exhaust line, while flue gascondensate 1113 is removed from the boiler bottom through a separateline.

Some Illustrative Alternative Embodiments

Various alternative embodiments are envisioned to be within the scope ofthe present invention. Some of these illustrative alternativeembodiments are described below. Other embodiments not described herewill also be apparent to one of ordinary skill in the art.

Single-Pipe Vapor Vacuum System Integration with Condensing Boilers

Sixth is presented a single-pipe vapor vacuum system integration with acondensing boiler. FIG. 12 illustrates a single-line vacuum system whichmay be integrated with a condensing boiler. A single-pipe system ispartitioned into section 1201 and section 1202 using a manifold (or setof valves) 1203. When section 1201 is in heating cycle, section 1201 isconnected to the evaporating section of a condensing boiler 1206 by themanifold 1203. When section 1202 is in cooling cycle, condensatereleased from radiators R1203 and R1204 flows through heat activatedvalves 1204 and accumulates above backflow valve 1205 leading to thecondensing section of the boiler 1206. If required, vacuum in coolingsection 1202 can be restored by a vacuum pump 1207. Line pitching 1208is provisioned for proper condensate flows. When the cycle is reversedon sections 1201 and 1202, condensate accumulated above backflow valve1205 flows into the condensing section of the boiler 1206.

Accordingly, another embodiment of the present invention is a heatingsystem having a closed-loop single-pipe vapor vacuum distribution systemhaving periodic condensate return and a vacuum condensing boiler, thesystem comprising a vapor source adapted to generate vapor, the vaporsource comprising an evaporating section and a condensing section; oneor more radiators; a feeder conduit connecting said vapor source to saidradiators; a return conduit for returning condensate from each radiatorback to said vapor source, wherein said return conduit contains no steamtraps; a vacuum pump to evacuate air from the system to a vacuum level,wherein the vapor source, the feeder conduit, and the return conduit areair-tight; a temperature sensor adapted to sense a temperature of thevapor leaving the vapor source; a pressure sensor adapted to sense apressure of the vapor source; and a control unit for controlling thevacuum condensing boiler and the vacuum pump based on the temperatureand the pressure sensed by the temperature sensor and the pressuresensor to maintain a consistent vacuum level and a consistenttemperature of the vapor, wherein the return conduit returns saidcondensate from the radiators to the condensing section at a temperaturebelow approximately 100° F. sufficient for condensing water from fluegas from a burner in the vapor source.

Alternative Temperature-Regulated Radiator Design

FIG. 13 illustrates an alternative embodiment of a temperature-regulatedradiator 1301 design according to yet another embodiment of the presentinvention. A temperature-regulated valve 1302 controls heat supply intoradiator 1301 based on a signal from temperature sensing element 1304located in a space to be heated and connected to valve 1302 by capillary1303. The sensing element 1304 setting is set to about 100° F. andattached to the radiator by sliding bar 1306. Heat supply into theradiator is controlled by temperature sensing element 1304 along slidingbar 1306; at the same time, the temperature of condensate return islimited to about 100° F. to ensure maximum condensing efficiency of theboiler. Configuration A shows radiator open when preset area is notheated yet, and configuration B shows radiator closed when preset areais heated.

Accordingly, another embodiment of the present invention is a radiatorcomprising a temperature regulated valve on a vapor supply line into theradiator which is closed by a signal from a temperature sensing mediaattached to the radiator, wherein the temperature sensing media issliding along the radiator height in order to control which portion ofthe radiator is employed for heat delivery.

In one alternative embodiment of the present invention, the temperatureregulated valve on the vapor supply line comprises an induction coilaround a plastic cylinder, a magnet, a spring, and a retractablemechanism in order to close the vapor supply line by the magnet by asignal from the temperature sensing media.

Multiple-Pass Condensing Vacuum Boilers

In some embodiments of the present invention, vacuum condensing boilershaving multiple passes designs. Proposed in FIGS. 11 and 12 were designsof vacuum condensing boilers with single-pass flue gas flow. Like hotwater condensing boilers, two- and three-flue gas passage designs can beforeseen for the purpose of compact design and efficiency. Instead ofusing a single-pass flow of flue gas from top to bottom as shown in FIG.11, flue gas flows in multiple passes from top to bottom, and back tothe top, as it exchanges heat with the condensate return. Such multiplepass embodiment can increase the efficiency of heat exchange and providefor a more compact design.

District Steam and Cogeneration Embodiments

According to one embodiment of the present invention, without changingthe system piping and radiators arrangement, heat from the district gridmay be utilized in place of the boiler. Accordingly, in one embodiment,a coil with district heating steam or hot water is used inside anevaporative heat exchanger in order to supply heat into the vapor vacuumheating system. Heating cycles of the vapor vacuum system are controlledby amount of steam/hot water supplied into an evaporative heatexchanger.

In another embodiment, exhaust from cogeneration Combined Heat and Power(CHP) system can be utilized in a heat exchanger/evaporator for thevapor vacuum systems proposed here. Any source of energy that canprovide steam can be utilized in the present invention, includingindustrial waste heat, solar, geothermal, etc.

Naturally-Induced Vacuum Embodiments

Finally is presented an embodiment of the present invention with anaturally induced vacuum. According to another embodiment, in place orin addition to a vacuum pump, the boiler operations may be cycled inorder to naturally induce and maintain a vacuum. For this purpose, anair vent/vacuum check valve set or a combined device is provisionedeither on each radiator or on the system air vent line connected to eachradiator. In the first heating cycle, the boiler is stopped whenthermostat's set temperature is achieved and the most distant radiatoris heated from top to bottom. The second condition is essential toverifying that the system is completely purged of air. In a cooledsystem, steam condenses inside and creates a vacuum, but the vacuumcheck valves will not let air in. Theoretically, system can create avacuum as low as 27 to 28.5 inches Hg when cooled down to 90-120° F.,correspondingly. Additionally, in some embodiments, a vacuum pump canalso be utilized for cold start of leak tight system and for convertedsteam system with minor leaks.

To take advantage of a vacuum in the system, the second and subsequentheating cycles are performed with a negative boiler cut off pressuresetting or setting lower than vacuum check valve cracking pressure. Ifrequired, the air purging cycle can be repeated at boiler cut offpressure setting higher than vacuum check valve cracking pressure. Thesystem is operated by automatic boiler controller in order to optimizeworking pressure/vacuum sequence.

The previously described vacuum single-pipe system of FIG. 1 which hasperiodic condensate return can be readily converted into a vapor vacuumsystem with naturally-induced vacuum by adding check valve to eachradiator air vent. The cycling boiler operations include the firstheating cycle at a pressure higher than the check valves' crackingpressure; vacuum formation in the closed, cooled system; and thesubsequent boiler operation set to vacuum or pressure below check valvescracking pressure. The radiator check valve can be installed eitherbefore or after the radiator vent valve on each radiator. If the vacuumcheck valve is installed before the radiator air vent valve, the airvent valve is not participating in the second and subsequent heatingcycles; so longer trouble-free operation time is expected. The radiatorvacuum check valves stay closed as long as the system operates undervacuum. Should any vacuum check valve fail, the corresponding air ventvalve will still be on guard to stop the steam from exiting theradiator; air will be sucked in through the faulty vacuum check valveafter every heating cycle and the system will start to function like aregular steam heating system.

In warm weather, complete system heating cycle, in order to purge thesystem of air and create a vacuum, is excessive. An auxiliary vacuumpump, connected to the system through control valve, can be provisionedto quickly restore vacuum in retrofitted system before heating cycle.Compared to known vacuum systems where high capacity vacuum pump is onand off during every heating cycle, vacuum pump of significantly lesscapacity, cost and maintenance operates only for approximately 10-15minutes to restore vacuum in the system. Then the boiler is cycled atcut off pressure higher than check valves' cracking pressure untilthermostat set temperature is achieved; air is completely purged fromthe system by that time. Vacuum emerges naturally afterwards in idlecooling system. A gas-fueled system with millivolt control, powered bypilot flame, is electricity independent and will maintain the vacuumwithout vacuum pump in case of power shortage.

By installing a check valve with 1 psi cracking pressure behind each airvent valve, a one-hundred-year-old residential single-pipe steam systemwhich had six radiators was converted by the inventor into a vacuumsystem with naturally induced vacuum. In test runs, 24 inch Hg vacuumwas produced in 80 minutes after the boiler stopped in the first heatingcycle. Vacuums of 22, 19 and 17 inch Hg were retained after 330, 260,and 165, correspondingly. This timing matches boiler day time cyclingfrequency during a cold season, but system ability to hold vacuumovernight is not sufficient. Either vacuum pump should be employed torestore vacuum in the morning or system should be purged from air duringfirst heating cycle at pressure higher then check valves crackingpressure.

An illustrative schematic for a large system with naturally inducedvacuum according to one embodiment of the present invention is shown inFIG. 14. Such a system includes a boiler 1401, radiators R1421-R1424,R1411-R1413, and R1401-R1402 with a radiator control valve 1403, aradiator condensate flow control valve 1404 and a radiator air ventvalve 1411 on each radiator. For the conversion of large existing steamsystems into vapor vacuum systems with a naturally-induced vacuum, asingle system vacuum check valve 1422, a system air vent valve 1421, anda system control valve 1423 may be utilized to improve reliability andleak detection. To protect the system from radiator vacuum check valvefailure/leakage, lines from each radiator air vent 1411 are connected tothe system's only vacuum check valve 1422. The on and off control valve1423 is in sync with the boiler operation and can be used instead of orin addition to the system vacuum check valve 1422 and for routine systempressure leak tests. Similarly, the system's air check valve 1421 wouldsecure system against radiators' air vent valve failure; faulty valvescan easily be traced by monitoring the temperature of the lines. Aspreviously discussed, vacuum was created initially and restored (ifnecessary) by vacuum pump 1406 connected through a vacuum pump controlvalve 1407. Line pitching 1408 is provisioned for proper condensateflows.

Due to heat loss in a long supply lines, too much steam may condense onconduit walls. Intermediate condensate drippings 1426 and 1427 into wetreturn 1424 are shown: from up feed riser 1425 and from a group of upperfloor radiators (R1411, R1412, R1413), respectively. For radiatorsR1421-R1424, a separate condensate return through the line with a floatcheck valve 1428 on each radiator is shown. Radiators R1401 and R1402are closest to the boiler 1401 and have short supply lines.

Without changing the system piping and radiator arrangement, steam fromthe district grid may be utilized in place of the steam boiler in avacuum system with a naturally induced vacuum. The vapor heating systemwith a naturally induced vacuum may be integrated into a district steamheating system in one of two ways:

(1) Single loop (direct steam usage): After pressure reduction, thedistrict steam is throttled into a vapor heating system with anaturally-induced vacuum. The amount of steam is controlled in order tokeep the heating system at the desired vacuum level. A water pump wouldbe provisioned in such system in order to return excessive condensateinto a district steam heating system

(2) Separate loop (indirect steam usage): A coil with high-pressuredistrict steam is used inside an evaporative heat exchanger to get thevapor heating system started with naturally-induced vacuum.

Depending on the particular system specifics, an automatic boilercontroller would perform the following functions:

(1) Vacuum pump switch on/off to restore a vacuum in the idle cooledsystem.

(2) First boiler heating cycle at switch off pressure slightly higherthan vacuum check valve cracking pressure.

(3) Temperature control of the most distant radiator as an indication ofthe complete air removal from the system.

(4) Monitoring the speed of the vacuum formation in a system.

(5) Second and subsequent heating cycles operate at the boiler cut-offpressure below vacuum check valves cracking pressure; the warmer theweather outside, the less cut-off pressure is utilized and the lower isthe steam/vapor temperature.

(6) Low water shut off device to prevent boiler overheating.

(7) Air vent line temperature monitoring to detect radiators air ventfailure.

The boiler controller may be integrated into the building control systemin order to optimize operation. One high power boiler can be replaced bya set of smaller capacity boilers fired up alone or in a group to saveenergy, as well as to allow ease of maintenance and emergency repairs.

Control Logic for Boiler and Radiators

According to one illustrative embodiment of the present invention, apossible boiler control logic is shown in Table 2.

According to one embodiment of the present invention, vacuum heatingsystem control includes several conditional loops to switch the boilerON and OFF. The boiler is ON if all of the following conditions are met:

-   -   House temperature is below set temperature by predetermined        offset temperature;    -   Vapor temperature at the boiler exit is below a set temperature;        and    -   Water level in the boiler is higher than a low water cut off        setting.

The house temperature controller follows day/time/temperature settingsto keep temperature within house comfortable during day time and lowerat night to save energy. The vapor temperature at the boiler exit isadjusted depending on the outside temperature, the colder the outsidetemperature the higher the vapor temperature at the boiler exit. Theboiler is switched ON and OFF to maintain the vapor set temperatureduring the heating cycle. Water cut off setting is set by the boilermanufacturer.

Only when the boiler is OFF and cooled below 100° F.—usually in thenight or early in the morning—the vacuum level is checked routinely andrestored if required. The vacuum pump is turned ON if all of thefollowing conditions are met:

-   -   Boiler is OFF;    -   Boiler temperature is below 100° F.; and    -   Vacuum in the system is below a pressure switch setting,        preferably in the range of 25-28 inch Hg, and even more        preferably at the highest possible pressure setting.

The vacuum pump restores vacuum level in the system up to the pressureswitch setting, and is switched OFF and disconnected after this level isreached. Depending on the system's leak tightness, pump may be turned ona daily, weekly, or monthly basis.

In one embodiment of the present invention, the vacuum level in thesystem is constantly monitored based on pressure in the system and vaportemperature at the boiler exit. In air tight system, these parametersfollow the saturated steam temperature table within 1° F. difference.Air presence in the system reduces the temperature of the saturatedvapor, the more air, the bigger the deviation. Based on Dalton's law ofPartial Pressures, in temperature interval of 140-212° F. a deviation of12-18° F. corresponds roughly to 30% air presence in the system and canbe used for alarm notice and mandatory system stop for leak search andto restore vacuum in the system. This logic can be incorporated into theboiler controller to constantly monitor the deviation between vaportemperature at the boiler exit from the steam table value of saturatedsteam at current pressure. When compared to the values recorded at theboiler fresh start, this data provides valuable information aboutchanges in the system tightness.

The house controller is usually installed in the farthest room which isthe last room to receive heat. Additionally, radiators in other roomscan be furnished with individual room controllers.

For vacuum heating systems working with regular boiler, a control valveon radiator supply line is switched ON and OFF by the room controllerdepending on temperature in the room and a float ball check valve oneach radiator is used to prevent vapor entering into condensate returnline.

For vacuum heating systems working with a condensing boiler, control ofheat supply into radiators per room base requires one of the following:

-   -   Control valve on radiator supply (feeder) line connected to room        controller and HAV on condensate return line;    -   Radiator build-in HAV on condensate exit line; or    -   Control valve on radiator supply (feeder) line connected to a        sensing element which is set to around 100° F. and slides along        radiator height.

TABLE 2 Illustrative Control Logic System settings: Boiler is switchedON when difference between temperature in a most distant room (T_(room))and a set temperature (T_(set)) is more than 3° F. Vapor from boilerupper temperature (193° F.), lower temperature (179° F.) are chosendepending on outside temperature (14° F. temperature offset) Initialsystem vacuum of 28 inch Hg Operational procedure: While differencebetween temperature in a most distant room T_(room) and T_(set) is morethan 3° F., room controller switch boiler ON Boiler start oscillating IFvapor temperature on boiler exit > 193° F., boiler OFF IF vaportemperature on boiler exit < 179° F., boiler ON When temperature in amost distant room T_(room) is equal to T_(set), room controller switchboiler OFF IF vapor temperature on boiler exit is less than 100° F. IFvacuum level less than 20″Hg, alarm “Time to check system for leaks” IFvacuum level is less than 28″Hg, vacuum switch ON to start vacuum pump(solenoid valve OPEN and vacuum pump ON) IF vacuum level is 28″Hg,vacuum switch OFF to stop vacuum pump (solenoid valve CLOSE and vacuumpump OFF) - Vacuum restored, system waiting for thermostat callsIndustrial Applications and Advantages of the Present Invention

Compared to a hot water heating system with a condensing boiler, theproposed system:

(1) Has higher energy value heat which is delivered into the radiatorsby vapor.

(2) Employs no hot water circulators, bypass valves, expansion tank,etc.

(3) Has less condensing coil length.

(4) Has less water in the boiler.

(5) Will not require expensive building repairs if leakage occurs.

(6) Has less electricity dependency.

(7) Has no frozen pipe problems and expensive repairs caused by powershortage.

(8) Requires no mechanical floor every 15-20 floors for high risebuilding to pump hot water.

Regular non-condensing boilers can be integrated into a two-pipe vaporvacuum heating system as well. The condensing section exclusion from theboiler would cause a decrease in the energy efficiency of the system,but would benefit the boiler maintenance, life expectancy, and cost.

CONCLUSION Prior Art Teaches Away

While vapor (steam) heating is well known, it has long been known andbelieved that vapor heating systems deliver hot condensate above 100° F.Since conventional condensing boilers require condensate returntemperatures below 100° F., the prior art has taught away from utilizingcondensate from vapor heating systems with condensing boilers. Theinventor has recognized the aforementioned problem in the prior art, andhas developed several methods and systems to lower the condensate returntemperature as described above. When used alone or in combination, thevarious methods allow vacuum heating systems to be integrated withcondensing boilers for the first time.

Furthermore, unlike conventional steam and vacuum vapor systems, nosteam traps are required in the present invention. The prior art teachesaway from the present invention by requiring steam traps.

The prior art has also never disclosed vapor vacuum condensing boilers,and taught away from their use.

While the methods disclosed herein have been described and shown withreference to particular operations performed in a particular order, itwill be understood that these operations may be combined, sub-divided,or re-ordered to form equivalent methods without departing from theteachings of the present invention. Accordingly, unless specificallyindicated herein, the order and grouping of the operations is not alimitation of the present invention.

While the present invention has been particularly shown and describedwith reference to embodiments thereof, it will be understood by thoseskilled in the art that various other changes in the form and detailsmay be made without departing from the spirit and scope of the presentinvention.

What is claimed is:
 1. A heating system integrating a closed-looptwo-pipe vapor vacuum distribution sub-system having periodic condensatereturn and a vacuum condensing boiler, the heating system comprising: avapor source adapted to generate vapor, the vapor source comprising aboiler, said boiler comprising an evaporating section and a condensingsection; one or more radiators comprising a heat activated valve at anexit from each radiator, the heat activated valve set to close atapproximately 100° F. to prevent hot condensate from entering thecondensing section; a feeder conduit connecting said vapor source tosaid radiators; a return conduit for returning condensate from eachradiator back to said vapor source, wherein said return conduit containsno steam traps; a vacuum pump to evacuate air from the system to avacuum level, wherein the vapor source, the feeder conduit, and thereturn conduit are air-tight; a temperature sensor adapted to sense atemperature of the vapor leaving the vapor source; a pressure sensoradapted to sense a pressure of the vapor; and a control unit forcontrolling the vapor source and the vacuum pump based on thetemperature and the pressure sensed by the temperature sensor and thepressure sensor to maintain a predetermined vacuum level and apredetermined temperature of the vapor, wherein the return conduitreturns said condensate from the radiators to the condensing section ata temperature below approximately 100° F. sufficient for condensingwater from flue gas from a burner in the vapor source.
 2. The system ofclaim 1, wherein air is evacuated by the vacuum pump when the vaporsource is idle at a vapor source temperature below approximately 100° F.when the vacuum level measured by the pressure sensor is below apredetermined threshold.
 3. The heating system of claim 1, furthercomprising: a thermostat in a space to be heated, wherein the vaporsource is switched on and off by the control unit until a temperature inthe space to be heated is equal to a thermostat set temperature.
 4. Thesystem of claim 1, further comprising: a backflow valve on a condensatereturn line at an entrance into the condensing section to prevent waterbackflow into the condensate return line.
 5. The system of claim 1,wherein the vacuum level in an idle system at a temperature in thevacuum condensing boiler below approximately 100° F. is up to 29 inchesHg.
 6. The heating system of claim 1, wherein the vacuum level and acorresponding temperature of the vapor source are adjusted based on anoutside temperature, and wherein a lower outside temperature results ina higher operating pressure and corresponding higher temperature of thevapor source.
 7. The heating system of claim 1, wherein at least oneradiator comprises a build-in heat activated valve adapted to close aradiator entrance when a condensate return temperature exceedsapproximately 100° F.
 8. The heating system of claim 7, wherein thebuild-in heat activated valve comprises a capsule positioned at theradiator bottom and filled with a low boiling fluid, and wherein saidcapsule is connected by a capillary to a bellow which expands and closesthe radiator entrance when the capsule is heated above a settemperature.
 9. The heating system of claim 1, further comprising: a setof valves adapted to split the system into a heated part, connected tothe evaporating section, and a cooling part, connected to the condensingsection, wherein a movement of the set of valves reconnects the coolingpart to the evaporating section and the heated part to the condensingsection, reversing system operation, without stopping the vapor sourceoperation.
 10. The heating system of claim 1, wherein the feeder conduitfrom the vapor source to the radiators and the return conduit are madefrom thermoplastic tubing.
 11. The heating system of claim 1, whereinthe vapor source further comprises: a combustion chamber at the burnerend for burning fuel with air and generating hot flue gas; acounter-current heat exchanger around the combustion chamber in theevaporating section for exchanging heat between the flue gas andevaporating water; and a second heat exchanger in the condensing sectionfor exchanging heat between the flue gas and incoming low-temperaturecondensate return having a temperature below approximately 100° F.,generating flue gas condensate.
 12. The heating system of claim 1,wherein the control unit further comprises program code, which whenexecuted causes the system to perform a process wherein the vacuum levelis checked routinely and restored if necessary, the process comprising:turning on the vacuum pump when the vapor source is off, a vapor sourcetemperature is below 100° F., and the vacuum level in the system isbelow a pressure switch setting.
 13. The heating system of claim 1,wherein the control unit further comprises program code, which whenexecuted causes the system to perform a process wherein leak tightnessof the system is checked, the process comprising: monitoring the vacuumlevel in the system based on the pressure in the pressure sensor and thetemperature in the temperature sensor; and activating an alarm when thetemperature of the vapor at the pressure sensed by the pressure sensordeviates by more than 10° F. from a steam table value of a saturatedsteam temperature at the sensed pressure.
 14. A heating system having aclosed-loop two-pipe vapor vacuum distribution sub-system havingperiodic condensate return, the heating system comprising: a vaporsource adapted to generate vapor, the vapor source comprising a boiler,said boiler comprising an evaporating section and a condensing section;one or more radiators, each radiator comprising a float check valve on aradiator condensate return line adapted to periodically returncondensate from the radiator at a temperature below approximately 100°F., wherein at least one radiator entrance comprises a control valveadapted to control vapor flow into the radiator based on a temperaturein the radiator's location; a feeder conduit connecting said vaporsource to said radiators; a return conduit for returning condensate fromeach radiator back to said vapor source, wherein said return conduitcontains no steam traps; a vacuum pump to evacuate air from the system,wherein the vapor source, the feeder conduit, and the return conduit areair-tight; a temperature sensor adapted to sense a temperature of thevapor leaving the vapor source; a pressure sensor adapted to sense apressure of the vapor; and a control unit for controlling the vaporsource and the vacuum pump based on the temperature and the pressuresensed by the temperature sensor and the pressure sensor to maintain apredetermined vacuum level and a predetermined temperature of the vapor.15. The system of claim 14, wherein air is evacuated by the vacuum pumpwhen the vapor source is idle when the pressure sensed in the pressuresensor is above a predetermined threshold.
 16. The system of claim 14,further comprising: a backflow valve on a condensate return line of thevapor source to prevent water backflow into the condensate return line.17. The system of claim 14, wherein the vacuum level in an idle systemat a temperature in the vapor source below approximately 100° F. is upto 29 inches Hg.
 18. The heating system of claim 14, wherein the vacuumlevel and a corresponding temperature of the vapor source are adjustedbased on an outside temperature, and wherein a lower outside temperatureresults in a higher operating pressure and corresponding highertemperature of the vapor source.
 19. A heating system having aclosed-loop two-pipe vapor vacuum distribution sub-system, the heatingsystem comprising: a boiler adapted to generate vapor, the boilercomprising a burner, an evaporating section and a condensing section;one or more radiators; a feeder conduit connecting said evaporatingsection of said boiler to said radiators; a return conduit for returningcondensate from each radiator back to said condensing section of saidboiler at a return condensate temperature below approximately 100° F.sufficient for condensing water from flue gas from the burner in theboiler; and a vacuum pump to evacuate air when the boiler is idle to avacuum level of at least 20 inches Hg at a vapor temperature belowapproximately 100° F., wherein the boiler, the feeder conduit, and thereturn conduit are air-tight.
 20. The system of claim 19, furthercomprising: a backflow valve on a condensate return line of the boilerto prevent vapor from entering the condensate return line.
 21. Thesystem of claim 19, further comprising: a thermostat in a space to beheated, wherein the boiler is switched on and off by a control unituntil a temperature in the space to be heated is equal to a thermostatset temperature.
 22. The system of claim 19, wherein the vacuum level inan idle system at a temperature in the boiler below approximately 100°F. is up to 29 inches Hg.
 23. The system of claim 19, wherein the vacuumlevel and a corresponding temperature of the boiler are adjusted basedon an outside temperature, and wherein a lower outside temperatureresults in a higher operating pressure and corresponding highertemperature of the boiler.
 24. The system of claim 19, wherein at leastone radiator comprises a build-in heat activated valve adapted to closea radiator entrance when a condensate return temperature exceedsapproximately 100° F.
 25. The system of claim 24, wherein the build-inheat activated valve comprises a capsule positioned at the radiatorbottom and filled with a low boiling fluid, and wherein said capsule isconnected by a capillary to a bellow which expands and closes theradiator entrance when the capsule is heated above a set temperature.26. The system of claim 19, further comprising: a set of valves adaptedto split the system into a heated part, connected to the evaporatingsection, and a cooling part, connected to the condensing section,wherein a movement of the set of valves reconnects the cooling part tothe evaporating section and the heated part to the condensing section,reversing system operation, without stopping the boiler operation. 27.The system of claim 19, wherein the feeder conduit from the boiler tothe radiators and the return conduit are made from thermoplastic tubing.28. The system of claim 19, wherein the boiler further comprises: acombustion chamber at the burner end for burning fuel with air andgenerating hot flue gas; a counter-current heat exchanger around thecombustion chamber in the evaporating section for exchanging heatbetween the flue gas and evaporating water; and a second heat exchangerin the condensing section for exchanging heat between the flue gas andthe incoming low-temperature condensate return having a temperaturebelow approximately 100° F., generating flue gas condensate.
 29. Thesystem of claim 19, further comprising: a temperature sensor adapted tosense a temperature of the vapor leaving the boiler; a pressure sensoradapted to sense a pressure of the vapor; and a control unit forcontrolling the boiler and the vacuum pump based on the temperature andthe pressure sensed by the temperature sensor and the pressure sensor tomaintain a predetermined vacuum level and a predetermined temperature ofthe vapor.
 30. The system of claim 29, wherein the control unit furthercomprises program code, which when executed causes the system to performa process wherein the vacuum level is checked routinely and restored ifnecessary, the process comprising: turning on the vacuum pump when theboiler is off, a boiler temperature is below 100° F., and the vacuumlevel in the system is below a pressure switch setting.
 31. The systemof claim 29, wherein the control unit further comprises program code,which when executed causes the system to perform a process wherein leaktightness of the system is checked, the process comprising: monitoringthe vacuum level in the system based on the pressure in the pressuresensor and the temperature in the temperature sensor; and activating analarm when the temperature of the vapor at the pressure sensed by thepressure sensor deviates by more than 10° F. from a steam table value ofa saturated steam temperature at the sensed pressure.